The prior art includes brushless D.C. motors which include switching circuits operated by electric filament lamps or light emitted diodes a photo-sensitive element and a slotted disc which is carried on the shaft which also carries the rotor. One such example is shown in Wessels, U.S. Pat. No. 3,299,335. Such structures provide power to a predetermined stator winding as the rotor passes through a predetermined angular sector. A disadvantage of such structures is that the phototransistor or other light sensitive element which is used with the light source is relatively expensive. Another disadvantage is that the disc with slots or a lobed cam which is used in such structures must be assemblied with great precision to insure the proper angular relationship between the rotor and the photosensitive element. In addition, the cost of the disc as well as the assembly time is also significant since such motors must be produced at a highly competitive price. Still another problem with such known motors is that the switching time between predetermined angular sectors of the rotor travel is less than is preferred. Yet another disadvantage of the prior art photosensitive element is the difficulty of shielding the photosensitive element from stray light.
It is an object of the invention to provide apparatus which will very rapidly switch electrical power to the windings of the stator as the rotor passes through predetermined angular sectors.
It is another object of the invention to provide apparatus which will in addition be insensitive to stray electrical fields and stray light.
Another object of the invention is to provide apparatus which will have greater simplicity than the prior art structures which utilize a light sensitive element and which may be assembled with less difficulty.